Has anyone retrofitted their house with a high velocity air conditioning unit? I've been weighing my options and I think this is the way I want to go, especially after I had a wall damaged last year after a window unit wouldn't stop gushing condensation everywhere. I've read that the systems use tubing that's about 2"-3" in diameter versus the big clunky metal ductwork one often associated with central air conditioning.
I've called a couple of HVAC companies in this area and no one seems to have a clue what I'm talking about when I mention these systems.
To those who have one of these systems: how satisfied are you with it and how invasive was the installation? How did you find a contractor who knew what they were doing when it came to these systems?
Thanks!
High velocity air conditioning?
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1918ColonialRevival
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Gothichome
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Re: High velocity air conditioning?
Colonial, just watched a YouTube on this. Looks, sounds and functions a lot like the attic installed A/C units. They talk about it bringing the humidity down in the house. I would think just like normal A/C units the humidity I’d drawn out at the coils. Is this maybe a rebranding of standard attic installed air conditioning.
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GinaC
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Re: High velocity air conditioning?
I'm also interested in this, as my furnace will have to be replaced within the next five years and I'm considering adding air conditioning at the same time. My house is small and I don't want to mess up any of the original (hot air) furnace ductwork.
I'm wondering if they can they add air conditioning ductwork to the existing system, or do they have to run all new ducts through the house?
I'm wondering if they can they add air conditioning ductwork to the existing system, or do they have to run all new ducts through the house?
1939 Minimal Traditional
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mjt
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Re: High velocity air conditioning?
Gina - I've owned several homes with forced air heat. The AC used the same ductwork...
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GinaC
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Re: High velocity air conditioning?
mjt wrote:Gina - I've owned several homes with forced air heat. The AC used the same ductwork...
Thank you so much! That's one less thing for me to worry about.
1939 Minimal Traditional
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CS in Low Hud
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Re: High velocity air conditioning?
Hi 1918,
We installed the system you are describing 14 years ago - it's called a "High-velocity mini-duct system", and at the time, there were two companies that manufactured the components: Unico and SpacePac. There may be others now, not sure.
Anyway, the system is similar to a conventional forced air system, in that you have an outside compressor, and one indoor air handler per zone. In our case, that's in the attic. For cost reasons we elected for a single zone in our 2100 sqf two-story house, but if we had done two zones (upstairs and downstairs), the second air handler would have gone in the basement. That actually would have all but eliminated fishing ductwork through walls, so it would have been simpler.
Each room has 1 - 6 outlets about the size of a CD. Usually, these are in the ceiling, but these can also go in the floor or walls, since the warm or cool air is well circulated in the room. The air handler needs an intake vent with a filter. That's bigger, like a 2' square register. We put ours in the ceiling over the staircase where the old attic entrance was, and then relocated the attic access
The ductwork is all flexible tubing about 3"-4" in diameter, which can indeed be fished through the walls leaving plaster more-or-less intact. Each outlet has it's own dedicated mini-duct splitting off of the main trunk in the attic.
In our case, we added an addition to the house at the same time, and where possible, dropped the ducts into new walls. Where that was not possible, occasional holes needed to be made. For example, several mini-ducts were dropped down inside an existing 2nd-floor wall from the attic. A baseboard in the bedroom needed to be carefully temporarily removed, so the ducts could be dropped into the joist-bay below, then a small hole as created in the plaster ceiling in the living room to route the ducts in the proper direction along the joist bay. Again, if we had done two zones, we could have just put in floor outlets on the first floor, and avoided all the wall fishing.
We opted for both heat and AC, which is delivered through the same ductwork. These days they also make a humidifier module for the heating unit. I'd recommend this, as the heat is pretty drying. The system works great, and we've been very happy with it - especially the AC, where the dehumidifying aspect of the system really shines! The system is very quiet (you have to hold your hand up to the outlets in most rooms to even tell that it's on), except in the rooms directly under the air handler. In those rooms, it's about as noisy as a typical forced air system.
The best way to find a contractor who installs these systems, is to use the directory on the Unico or SpacePac website. At least that's what we did. We got bids from two companies, and went from there.
Feel free to ask me any other questions you might have.
Best,
Chris
We installed the system you are describing 14 years ago - it's called a "High-velocity mini-duct system", and at the time, there were two companies that manufactured the components: Unico and SpacePac. There may be others now, not sure.
Anyway, the system is similar to a conventional forced air system, in that you have an outside compressor, and one indoor air handler per zone. In our case, that's in the attic. For cost reasons we elected for a single zone in our 2100 sqf two-story house, but if we had done two zones (upstairs and downstairs), the second air handler would have gone in the basement. That actually would have all but eliminated fishing ductwork through walls, so it would have been simpler.
Each room has 1 - 6 outlets about the size of a CD. Usually, these are in the ceiling, but these can also go in the floor or walls, since the warm or cool air is well circulated in the room. The air handler needs an intake vent with a filter. That's bigger, like a 2' square register. We put ours in the ceiling over the staircase where the old attic entrance was, and then relocated the attic access
The ductwork is all flexible tubing about 3"-4" in diameter, which can indeed be fished through the walls leaving plaster more-or-less intact. Each outlet has it's own dedicated mini-duct splitting off of the main trunk in the attic.
In our case, we added an addition to the house at the same time, and where possible, dropped the ducts into new walls. Where that was not possible, occasional holes needed to be made. For example, several mini-ducts were dropped down inside an existing 2nd-floor wall from the attic. A baseboard in the bedroom needed to be carefully temporarily removed, so the ducts could be dropped into the joist-bay below, then a small hole as created in the plaster ceiling in the living room to route the ducts in the proper direction along the joist bay. Again, if we had done two zones, we could have just put in floor outlets on the first floor, and avoided all the wall fishing.
We opted for both heat and AC, which is delivered through the same ductwork. These days they also make a humidifier module for the heating unit. I'd recommend this, as the heat is pretty drying. The system works great, and we've been very happy with it - especially the AC, where the dehumidifying aspect of the system really shines! The system is very quiet (you have to hold your hand up to the outlets in most rooms to even tell that it's on), except in the rooms directly under the air handler. In those rooms, it's about as noisy as a typical forced air system.
The best way to find a contractor who installs these systems, is to use the directory on the Unico or SpacePac website. At least that's what we did. We got bids from two companies, and went from there.
Feel free to ask me any other questions you might have.
Best,
Chris
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1918ColonialRevival
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Re: High velocity air conditioning?
Thanks for all the responses. We have circulated hot water heat, which I'm not giving up, so the tubing would be for A/C only.
Placing a handler in the attic is unfortunately not a possibility, as our attic was finished as a maid's quarters when the house was built with two bedrooms, a full bath, and two storage areas that we use. For the time being, I may just consider adding it to the first floor, which is about 1800 square feet or so. The handler can go in the basement.
Chris - once I learn a little more about the systems, I'll probably be sending some questions your way.
Placing a handler in the attic is unfortunately not a possibility, as our attic was finished as a maid's quarters when the house was built with two bedrooms, a full bath, and two storage areas that we use. For the time being, I may just consider adding it to the first floor, which is about 1800 square feet or so. The handler can go in the basement.
Chris - once I learn a little more about the systems, I'll probably be sending some questions your way.
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mjt
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Re: High velocity air conditioning?
Like you, we had looked at high-velocity AC-only systems because we have hot water heat in our house. However, when we gutted our attic we installed a full forced-air HVAC unit in the attic and ran standard ductwork around the perimeter behind the kneewalls. We have two zones. One provides heat and AC in the attic with standard wall registers and the other AC for the second floor via ceiling vents.
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phil
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Re: High velocity air conditioning?
the thing with AC is the cold air wants to sink , and with heat it's the opposite. you can blow cold air in near a floor or heat in from the ceiling, it just isn't as efficient. maybe the higher air velocity helps. It might at times require a trade off to use the same piping.
I had been running an AC in my attic bedroom so that it's comfy for sleeping. I noted that the bedroom door is cut quite high, over an inch gap. I could feel all the AC pouring out under the door and spilling down the stairs. that's the only air return for heat so I guess it's a trade off. I guess I could close the gap with an added strip.
some of the new super well insulated houses implement a heat exchanger to allow the expended air to heat the incoming air. I guess the same would work to cool incoming air? us old house people really need to worry about that unless we seal like crazy.
I had been running an AC in my attic bedroom so that it's comfy for sleeping. I noted that the bedroom door is cut quite high, over an inch gap. I could feel all the AC pouring out under the door and spilling down the stairs. that's the only air return for heat so I guess it's a trade off. I guess I could close the gap with an added strip.
some of the new super well insulated houses implement a heat exchanger to allow the expended air to heat the incoming air. I guess the same would work to cool incoming air? us old house people really need to worry about that unless we seal like crazy.
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CS in Low Hud
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Re: High velocity air conditioning?
Hi 1918,
The system is modular, so in your case you would only need the AC portion of the air handler. The good news is that if you are only doing the first floor, and putting the air handler in the basement, there should be very little (or no) wall-fishing necessary. If you would be bringing AC to the second floor/attic floor, that would then obviously require some more effort. But, if you ARE only doing the first floor, you might find it simpler to just do a standard forced air system, like MJT. dunno.
Phil, you are certainly right about the high-velocity air helping to counteract the normal thermal attributes of a forced air system. That's factored into the design. The other factor is that most rooms, unless they are very small - like a powder room - will have multiple outlets. In a standard forced air system, you'd have just one. So, for example, our dining room is about 12' square. It has four ceiling outlets, one in each corner of the room, so the air in the room is well mixed as it leaves the outlets. I just took two instant-read thermometer readings in the center of the room, one at the floor, and one at the ceiling, and there is only a 2.5-degree difference. And that's on a cold day with the wind howling to beat the band! So... very, very even.
The big difference is the temperature between the first and second floors. This is a result of only doing a single zone. It's probably 5 degrees warmer upstairs right now, and in the summer, with the AC, that would also be the case. You can counteract these tendencies somewhat by plugging some vent outlets, so we usually block a couple upstairs during the heating months, and a couple downstairs during the cooling months, otherwise the differential would be more like 10 degrees.
For what it's worth, the heating unit is circulated hot water, so if on down the road, you wanted to add a heating unit, that could probably be done without too much fuss.
Best,
Chris
The system is modular, so in your case you would only need the AC portion of the air handler. The good news is that if you are only doing the first floor, and putting the air handler in the basement, there should be very little (or no) wall-fishing necessary. If you would be bringing AC to the second floor/attic floor, that would then obviously require some more effort. But, if you ARE only doing the first floor, you might find it simpler to just do a standard forced air system, like MJT. dunno.
Phil, you are certainly right about the high-velocity air helping to counteract the normal thermal attributes of a forced air system. That's factored into the design. The other factor is that most rooms, unless they are very small - like a powder room - will have multiple outlets. In a standard forced air system, you'd have just one. So, for example, our dining room is about 12' square. It has four ceiling outlets, one in each corner of the room, so the air in the room is well mixed as it leaves the outlets. I just took two instant-read thermometer readings in the center of the room, one at the floor, and one at the ceiling, and there is only a 2.5-degree difference. And that's on a cold day with the wind howling to beat the band! So... very, very even.
The big difference is the temperature between the first and second floors. This is a result of only doing a single zone. It's probably 5 degrees warmer upstairs right now, and in the summer, with the AC, that would also be the case. You can counteract these tendencies somewhat by plugging some vent outlets, so we usually block a couple upstairs during the heating months, and a couple downstairs during the cooling months, otherwise the differential would be more like 10 degrees.
For what it's worth, the heating unit is circulated hot water, so if on down the road, you wanted to add a heating unit, that could probably be done without too much fuss.
Best,
Chris